Of course, we know it sounds unbelievable. But you really can measure the entire Earth - the whole, giant planet that we all live on - using just an ordinary 12-inch ruler.

Eratosthenes Original Experiment was Ingenious

Methods for everyone
Whether you love science, or just think doing this would be cool. Perfect for museums and classrooms. For children everywhere. Or measure the Earth in the 'shadow' of a person or event that's important to you. Literally, a world of possibilities.

Long ago, in ancient Alexandria, there lived a librarian named Eratosthenes. And he had heard a remarkable story, about a town with no shadows.

If you like science, you're going to find this fascinating. But we want everyone to try. Not just science-types. So think, a bunch of school kids. Or a family on a picnic. Two shop clerks at lunch. Or a farmer in his field
What a wonderful way
To discover that 'science' isn't something big or distant. Or...

I stood beneath the giant globe at the old New York World's Fair, amazed by the wonders all around me. So I guess it makes sense that I'd grow up to be an aerospace engineer, and then find a way to measure the Earth.